1. Field of the Invention
The present invention relates to a relay server and a relay communication system, which enable a client terminal connected to a remote local area network (LAN) to communicate beyond a wide area network (WAN).
2. Description of the Related Art
Client terminals connected to remote LANs sometimes communicate with one another beyond a WAN. The virtual private network (VPN) can construct a network that appears as if the remote LANs were directly connected to each other. However, it is difficult for the VPN to construct a network having expandability and flexibility.
A relay communication system disclosed in Japanese Patent Laid-Open Publication No. 2008-129991 can construct a network that appears as if the remote LANs are directly connected to one another in a similar way to the VPN. Then, unlike the VPN, it is easy for the relay communication system to construct the network having expandability and flexibility.
The relay communication system includes a WAN and a plurality of LANs. Each of the LANs includes a relay server. Each relay server stores relay group information regarding relay servers provided in the relay communication system and shared resource information regarding resources shared in the relay communication system.
When a client terminal connected to one of the LANs manipulates resources stored by client terminals of other LANs, the relay servers connected to these LANS relay the manipulation for the resources based on the relay group information and the shared resource information.
The number of LANs provided in the relay communication system may sometimes be increased or reduced. The resources shared in the relay communication system may sometimes be updated. However, the relay communication system can update the relay group information and the shared resource information in response to these changes. Then, the relay communication system can construct the network having expandability and flexibility in response to these changes.
In the relay communication system disclosed in Japanese Patent Laid-Open Publication No. 2008-129991, a change may occur in the number of LANs and client terminals, and in the connection state between the LANs and the client terminals. However, Japanese Patent Laid-Open Publication No. 2008-129991 does not disclose the specific means for confirming in real time such changes in the number and the connection state of the LANs and the client terminals in the event that the client terminals and the relay servers designate destinations for communication. Moreover, Japanese Patent Laid-Open Publication No. 2008-129991 does not disclose any specific means capable of dynamically allocating virtual IP (internet protocol) addresses to the client terminals and the relay servers even if changes in the number and the connection state of the client terminals and the relay servers occur.